CN104202813A - Cognitive radio network clock synchronization method based on double control channel mechanism - Google Patents

Abstract

The invention belongs to the field of wireless communication signal processing and discloses a cognitive radio network clock synchronization method based on a double control channel mechanism. The method includes firstly, performing the neighbor / level discovery and clock synchronous initialization based on the low-level control channel; secondly, performing the rough clock synchronization based on the low-level control channel; thirdly, performing the fine clock synchronization based on the high-level control channel. According to the method, the control channel establishment of a radio network is combined with the clock synchronization organically, the time information of the process of clock synchronization can be obtained owing to the establishing process of the control channels, the control channel establishment can be accelerated, the usability of the radio network in the segment of network establishment can be improved, and the application of the cognitive radio network can be promoted.

Description

Cognitive radio networks clock synchronizing method based on double-deck control channel mechanism

Technical field

The invention belongs to wireless communication signals process field, be specifically related to a kind of cognitive radio networks clock synchronizing method.

Background technology

Cognitive radio networks (Cognitive Radio Network, CRN) is a kind of novel wireless network communications system, and it consists of wireless connections the cognitive radios that is called cognitive user (Cognitive User, CU).Cognitive radio networks exists different greatly from the operational mode of conventional wireless communication network, it can be called primary user (Primary User, PU) conventional wireless communication equipment and coexistence of systems thereof, in the same radio frequency band of the same area, and do not cause adverse effect to the latter.Setting up and moving does not need before cognitive radio networks to the application working frequency range mandate of local radio spectrum management department the mandate of small part frequency range (or only need).This characteristic of cognitive radio networks causes extensive, the lasting and close concern of academia, industrial quarters, commercialization and military user and radio control department of various countries of wireless communication field, and correlation technique is rapid in development in recent years.

Technical, cognitive radio networks is set up and effectively moved to safety roughly needs following steps: first, the cognitive user in network is utilized the means such as spectral sensor and network data base to collect and analyze local wireless frequency spectrum and used state information, detects the conventional wireless device of periphery; Afterwards, carry out decision-making according to the communication requirement of cognitive radio networks, work up follow-up radio course of an action; Finally, by wireless waveform and the communication protocol of applying flexible, all cognitive user in cognitive radio networks are implemented above-mentioned radio course of an action harmoniously and are completed network service task.

Realize above-mentioned technological approaches and need to solve multiple key technical problems, comprise detection and identification and the clock synchronization of ad etc. of wireless frequency spectrum monitoring, the parameter Estimation of wireless channel, adjacent cognitive user.Because cognitive radio networks does not have the use authority use authority of few part frequency (or only have) of fixed frequency range, therefore address these problems and there is great technical difficulty.Especially, at the initial establishment stage of cognitive radio networks, on the one hand due to cognitive user lack available frequency, network topology and network time the key message such as benchmark, on the other hand, for avoiding the interference to primary user, the communication supplementary meanss such as cognitive user can not be used conventional channel detection, the signaling of shaking hands, the challenge of above-mentioned technical problem is particularly outstanding.This class problem is referred to as " cognitive radio networks is set up problem " (setting up problem hereinafter to be referred as network) by academia, and launched research widely.

In earlier stage, we set up problem for network and have proposed the network creating method based on double-deck control channel mechanism and obtained national inventing patent (patent No. ZL 201110259192.4).The major technique thinking of the method is that control channel is divided into the limited low layer control channel of power spectral density (Lower Level Control Channel, and the high-rise control channel of high channel capacity (Higher Level Control Channel LLCC), HLCC), in two kinds of control channels, adopt different wireless waveform and communication protocol, can effectively reduce network and set up the technical difficulty of problem.In low layer control channel, adopt the Waveform Design of interference temperature restriction can ensure that cognitive user and primary user coexist in the same frequency range of the same area, cognitive radio networks can be set up and continuous service under the condition that lacks spectrum authorization.Realize at low layer control channel on the basis of basic control information exchange, further set up high-rise control channel, expand control channel coverage and improve control information exchange rate, thereby substep is realized effective foundation of cognitive radio networks.

In the cognitive radio networks research based on said method and application process, we find, clock synchronization of ad technology is to solve cognitive radio networks to set up one of necessary key technology of problem.Reason is as follows: first, the operation of cognitive radio networks depends on frequency spectrum perception, frequency spectrum uses information to be obtained by the spectral sensor that is distributed in each cognitive user, and for these spectrum informations of effective integration are to form the whole network idle frequency spectrum spatial and temporal distributions figure that can use, global synchronized timing system is essential.Secondly,, in order to utilize more efficiently the idle frequency range that detects, to set up the cognitive channel of high speed, raising whole network data throughput, between cognitive user, must possess time division multiplexing/duplex to cognitive channel machine-processed; Meanwhile, because the distribution of cognitive channel on time and space is all random, only has accuracy and the stability of setting up this time division multiplexing of the whole network clock synchronous guarantee/duplex mechanism.In addition, the whole network clock synchronous is undoubtedly favourable for key waveforms parameters such as extracting sign synchronization, bit synchronization, frame synchronization between cognitive user, can improve point-to-point transmission performance.

But, if clock synchronous process and the cognitive radio networks process of establishing based on double-deck control channel mechanism are separated to independent design, can find in fact to exist the relation that interdepends, mutually pins down between the two.On the one hand, the distribution of clock synchronization information and exchange depend on the foundation of high-rise control channel.Due to the waveform power limited of low layer control channel, cause that its coverage is little and channel capacity is lower, and share use by multiple cognitive user by time division way, therefore it can only be used for realizing some business not high to data rate requirement, as neighbours/level survey (neighbor/hierarchy discovery) etc.For the whole network clock synchronous process, if only by low layer control channel, synchronization accuracy and refresh rate must be extremely restricted, and therefore need the support of IA High Speed Channel.On the other hand, the foundation of IA High Speed Channel depends on again the clock synchronization information of certain precision.For example, between adjacent cognitive user, need to consult in real time common available idle frequency, or be called frequency spectrum cavity-pocket (Spectrum Hole); The communication waveforms of high data rate and agreement need sign synchronization, bit synchronization, frame synchronization clock of degree of precision etc.

For above-mentioned consideration, we have further proposed a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism.The main technological route of the method is, first utilize LLCC that low speed control information exchange capacity is provided, in realizing the netinit processes such as neighbours/level detection, complete the whole network clock synchronous initialization procedure, and provide low precision clock synchronous to meet the needs of setting up high-rise control channel.Afterwards, in the process of establishing of high-rise control channel, realize high accuracy the whole network clock synchronous.With respect to traditional wireless network clock synchronizing method, the method can provide and keep the whole network clock synchronous in the process of establishing of double-deck control channel, and takes full advantage of the channel resource of double-deck control channel, progressively improves clock synchronization accuracy.This characteristic is for ensureing that the harmony of the wireless behavior of cognitive user in cognitive radio networks, the efficiency that raising network is set up and the stability of improving the network operation are all very helpful.

Summary of the invention

For the clock synchronization of ad problem in cognitive radio networks development and application, the invention discloses a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism, comprise the following steps:

If represent the cluster head local zone time of the n time cluster head broadcast, n is natural number; If in given user bunch, comprise at least one cognitive user in cognitive radio networks;

The first step, the neighbours/level based on low layer control channel is found and clock synchronous initialization;

(S11) step, establishes some cognitive user and waits for cluster head broadcast at low layer control channel, if cluster head broadcast do not detected, determines that this cognitive user is cluster head;

(S12) step, cluster head sends cluster head broadcast by low layer control channel, comprises No. ID and local transmitting time of this cognitive user in cluster head broadcast

(S13) step, the cognitive user except cluster head reads the time from cluster head broadcast and the time of advent of recording cluster head broadcast simultaneously return to the message or exit request message of joining request to cluster head, described in join request message or exit No. ID and the local transmitting time that request message comprises cognitive user

(S14) step, cluster head is received the message or exit request message of joining request from certain cognitive user by low layer control channel, and records this message time of advent now, cognitive user is denoted as a bunch member; Then, reply one to a bunch member who sends this message and comprise local transmitting time allow add message or allow exit message;

(S15) step, bunch member receives that allowing that cluster head in (S14) step replys adds message or allow after exit message, record local time of advent and read the time with by calculating the estimation initial value to cluster head timing parameter and bunch broadcast propagation delay

(S16) step, bunch member, by calculating the estimated value to cluster head clock, completes the clock synchronous initialization between bunch member and cluster head;

Second step, the clock based on low layer control channel is slightly synchronous;

(S21) step, cluster head periodically continues to send N-1 cluster head broadcast by low layer control channel, and comprises local transmitting time data in transmission message wherein, n={2 ..., N}, N is more than or equal to 2 natural number;

(S22) step, a bunch member receives cluster head broadcast, records local time of reception to be and read the time

(S23) step, the estimation initial value in conjunction with bunch member who obtains in the first step to cluster head local clock parameter Estimation initial value and bunch broadcast propagation delay, upgrades the timing parameter estimated value of bunch member to cluster head;

(S24) step, upgrades the estimated value of bunch member to cluster head local clock;

The 3rd step, the clock essence based on high-rise control channel is synchronous;

Be located in certain cluster of cognitive radio networks and have two bunches of members, be denoted as respectively CM _aand CM _b, and they have completed respectively the clock synchronous initialization of the described first step with cluster head and the clock of second step is slightly synchronizeed;

(S31) step, cluster head continues to send cluster head broadcast on low layer control channel, and in message with local zone time wherein, n ∈ N+1 ..., and N+m}, m is natural number;

(S32) step, CM _aand CM _bon low layer control channel, receive cluster head broadcast, read and record respectively time of reception and be with

(S33) step, CM _bon high-rise control channel to CM _asend with local zone time with the cluster head time send a request message;

(S34) step, CM _aon high-rise control channel, receive CM _bsend a request message, sign in and read the time data in sending a request message with according to cM _afrom local data base, find the corresponding cluster head broadcast time of advent

(S35) step, CM _ato CM _bsend one with with local transmitting time transmission grant message;

(S36) step, CM _breceive transmission grant message, record the local time of advent and read with

(S37) step, calculates CM _bwith CM _abetween the estimated value of relative time clock parameter;

(S38) step, calculates CM _bto CM _athe estimated value of local clock, completes CM _awith CM _bbetween clock based on high-rise control channel essence synchronizing process.

Further, (S15) step in the first step, compute cluster member is to cluster head local clock parameter Estimation initial value estimation initial value with bunch broadcast propagation delay be specially:

$\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}\end{array}\right]={\left({\left[B^{\left(1\right)}\right]}^T{B}^{\left(1\right)}\right)}^{-1}{\left[B^{\left(1\right)}\right]}^T{A}^{\left(1\right)},$

Wherein,

$A^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_1^{\left(1\right)}\\ T_4^{\left(1\right)}\\ T_5^{\left(1\right)}\end{array}\right],B^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{ccc}{T}_2^{\left(1\right)}& -1& -1\\ T_3^{\left(1\right)}& -1& +1\\ T_6^{\left(1\right)}& -1& -1\end{array}\right].$

Further, the concrete computational process of (S23) step in second step is:

${\widehat{\mathrm{\Θ}}}^{\left(n\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(n\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(n\right)}\end{array}\right]={\left({\left[B^{\left(n\right)}\right]}^T{B}^{\left(n\right)}\right)}^{-1}{\left[B^{\left(n\right)}\right]}^T{A}^{\left(n\right)},$

Wherein,

$A^{\left(n\right)}=\left[\begin{array}{c}{T}_1^{\left(1\right)}+{\hat{D}}^{\left(1\right)}\\ T_1^{\left(2\right)}+{\hat{D}}^{\left(1\right)}\\ .\\ .\\ .\\ T_1^{\left(n\right)}+{\hat{D}}^{\left(1\right)}\end{array}\right],B^{\left(n\right)}=\left[\begin{array}{cc}{T}_2^{\left(1\right)},& -1\\ T_2^{\left(2\right)},& -1\\ .& .\\ .& .\\ .& .\\ T_2^{\left(n\right)},& -1\end{array}\right],$

represent the n time estimated value of Θ, n={1 ..., N}, for timing parameter estimated value.

Further, the concrete computational process of (S24) step in second step is: wherein, represent the n time estimated value of the local clock of bunch member to cluster head, t _cMfor bunch member's clock value, for timing parameter estimated value.

Further, (S37) step computing formula in the 3rd step is:

${\widehat{\mathrm{\Φ}}}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}\\ {\widehat{\mathrm{\φ}}}_2^{\left(m\right)}\end{array}\right]={\left({\left[Q^{\left(m\right)}\right]}^T{Q}^{\left(m\right)}\right)}^{-1}{\left[Q^{\left(m\right)}\right]}^T{P}^{\left(m\right)},$

Wherein,

$P^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_{2,A}^{\left(1\right)}\\ .\\ .\\ .\\ T_{2,A}^{\left(N\right)}\\ T_4^{(N+1)}+T_5^{(N+1)}+T_{2,A}^{(N+1)}\\ .\\ .\\ .\\ T_4^{(N+m)}+T_5^{(N+m)}+T_{2,A}^{(N+m)}\end{array}\right],Q^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{cc}{T}_{2,B}^{\left(1\right)}& 1\\ .& .\\ .& .\\ .& .\\ T_{2,B}^{\left(N\right)}& 1\\ T_3^{(N+1)}+T_6^{(N+1)}+T_{2,B}^{(N+1)}& 3\\ .& .\\ .& .\\ .& .\\ T_3^{(N+m)}+T_6^{(N+m)}+T_{2,B}^{(N+m)}& 3\end{array}\right],$

represent CM _awith CM _breceive after the N+m time cluster head broadcast CM _awith CM _bbetween the m time relative time clock estimates of parameters.

Further, (S38) step computing formula in the 3rd step is: CM _bestimate CM _alocal clock ${\hat{t}}_{A,B}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}{t}_B{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}+{\widehat{\mathrm{\φ}}}_2^{\left(m\right)},$ Wherein, for CM _bwith CM _abetween the m time relative time clock estimates of parameters.

Basic ideas of the present invention are: the whole network clock synchronous process of cognitive radio networks is divided into three steps, is respectively: the discovery of neighbours/level and clock synchronous initialization based on LLCC, the thick clock essence synchronous and based on HLCC of clock based on LLCC is synchronous.The derivation of concrete principle and correlation computations formula is as follows:

Suppose, the imperfection of cognitive user local clock is modeled as clock skewing (Clock Skew) and clock skew (Clock Offset).Be any two cognitive user CR _iand CR _jlocal clock t _iand t _jbetween meet t _i=f _ijt _j+ τ _ij, wherein f _ijfor CR _iwith respect to CR _jclock skewing, τ _ijfor CR _iwith respect to CR _jclock skew.Between cognitive user, exchange is with the signaling message of local time stamp.According to the residing environment of cognitive radio networks, the one below the time delays variable that signaling message propagates into another user from a user can be modeled as two kinds of random processes: the i.e. Gaussian Profile random process of given average and exponential distribution random process.Due to the modeling pattern of time delays variable for cognitive user network set up and clock synchronizing process in method of operation do not affect, and only affect the final prediction equation of timing parameter, therefore in this article, detailed process of the present invention for convenience of description, derives as an example of Gaussian Profile random process example below.

The first step, the neighbours/level based on LLCC is found and clock synchronous initialization procedure.

For arbitrary given user bunch in cognitive radio networks, it comprises at least one cognitive user, and the operation of the discovery of neighbours/level and clock synchronous initial phase is as follows.LLCC adopts time division multiplexing mode, comprises three kinds of time slots, is respectively cluster head broadcast (CH Broadcasting, CHB) time slot, bunch member broadcast (Cluster Member Broasting, CMB) time slot and cluster head are responded (CH Answering, CHA) time slot.At CHB time slot, cluster head CH broadcasts with local zone time on LLCC cluster head broadcast, and other cognitive user CU intercepts this message at this time slot, and the CU local zone time of the cluster head broadcast that receives of record cH local zone time with the cluster head transmission broadcast reading from this message for the CU that wants to add or exit bunch, can be at CMB time slot, on LLCC, broadcast is with CU local zone time (Request To Join, the RTJ) message or exit request (Request To Quit, RTQ) message of joining request.Once CH receives RTJ or RTQ message, first recording messages time of advent then reply one with CH local zone time at CHA time slot just now the time of advent being recorded to allow add (Clear To Join, CTJ) message or allow to exit (Clear To Quit, CTQ) message.CU receive CTJ or CTQ just complete cognitive user bunch in level find, also want recording messages time of advent simultaneously and read cluster head and send the time in message with to complete the clock synchronous initialization between CH.Clock skewing and the clock skew of definition cluster head CH and certain bunch of member CM are respectively f and τ, cluster head clock t _cHclock t with bunch member _cMmeet following relation:

T _cH=(t _cM-τ)/f (formula 1)

And the time data that CM is recorded to meet following relation, wherein D ⁽¹⁾for message propagation time delay.

$\left\{\begin{array}{c}{T}_2^{\left(1\right)}=f(T_1^{\left(1\right)}+D^{\left(1\right)})+\mathrm{\τ}\\ T_3^{\left(1\right)}=f(T_4^{\left(1\right)}-D^{\left(1\right)})+\mathrm{\τ}\\ T_6^{\left(1\right)}=f(T_5^{\left(1\right)}+D^{\left(1\right)})+\mathrm{\τ}\end{array}\right.$ (formula 2)

(formula 2) can be rewritten as:

$\left\{\begin{array}{c}{T}_1^{\left(1\right)}=T_2^{\left(1\right)}{\mathrm{\θ}}_1-{\mathrm{\θ}}_2-D^{\left(1\right)}\\ T_4^{\left(1\right)}=T_3^{\left(1\right)}{\mathrm{\θ}}_1-{\mathrm{\θ}}_2+D^{\left(1\right)}\\ T_5^{\left(1\right)}=T_6^{\left(1\right)}{\mathrm{\θ}}_1-{\mathrm{\θ}}_2-D^{\left(1\right)}\end{array}\right.$ (formula 3)

Wherein θ ₁=1/f, θ ₂=τ/f.θ ₁, θ ₂represent timing parameter, represent θ ₁estimation initial value, represent θ ₂estimation initial value, (formula 3) be rewritten into matrix form be

Α ⁽¹⁾=B ⁽¹⁾x (formula 4)

Wherein,

$A^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_1^{\left(1\right)}\\ T_4^{\left(1\right)}\\ T_5^{\left(1\right)}\end{array}\right],B^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{ccc}{T}_2^{\left(1\right)}& -1& -1\\ T_3^{\left(1\right)}& -1& +1\\ T_6^{\left(1\right)}& -1& -1\end{array}\right],X\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}\end{array}\right]$

Therefore, can do following estimation to timing parameter:

$X=\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}\end{array}\right]={\left({\left[B^{\left(1\right)}\right]}^T{B}^{\left(1\right)}\right)}^{-1}{\left[B^{\left(1\right)}\right]}^T{A}^{\left(1\right)}$ (formula 5)

Thus, CM obtains the estimation initial value to CH local clock

Second step, the clock based on LLCC is slightly synchronous:

After the level completing in cognition network bunch is found and clock initialization, a bunch member CM obtains cluster head CH timing parameter θ ₁, θ ₂with propagation delay D ⁽¹⁾estimation initial value with meanwhile, CH continues to send CH broadcast by LLCC.Suppose that CH, completing after above-mentioned first step operation, continues again to have sent CH broadcast N-1 time, N is that value is more than or equal to 2 natural number; If the CH broadcast in the first step is also counted, the CH local zone time data in all CHB broadcasts can be designated as n ∈ [1, N].CM receives the broadcast of CH, and records the time of advent of each broadcast, is designated as n ∈ [1, N].The relation of CH clock and CM clock can be expressed as

$T_1^{\left(n\right)}+{\hat{D}}^{\left(1\right)}=\frac{T_2^{\left(n\right)}-\mathrm{\τ}}{f}+d^{\left(n\right)},n=\{\mathrm{1,2},...,N\}$ (formula 6)

Wherein, for the zero-mean random variable of Gaussian Profile.(formula 6) can be write as following matrix form.

Α ⁽ⁿ⁾=B ⁽ⁿ⁾Θ+d ⁽ⁿ⁾(formula 7)

Wherein,

$A^{\left(n\right)}=\left[\begin{array}{c}{T}_1^{\left(1\right)}+{\hat{D}}^{\left(1\right)}\\ T_1^{\left(2\right)}+{\hat{D}}^{\left(1\right)}\\ .\\ .\\ .\\ T_1^{\left(n\right)}+{\hat{D}}^{\left(1\right)}\end{array}\right],B^{\left(n\right)}=\left[\begin{array}{cc}{T}_2^{\left(1\right)},& -1\\ T_2^{\left(2\right)},& -1\\ .& .\\ .& .\\ .& .\\ T_2^{\left(n\right)},& -1\end{array}\right],\mathrm{\Θ}=\left[\begin{array}{c}{\mathrm{\θ}}_1\\ {\mathrm{\θ}}_2\end{array}\right]\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}\frac{1}{f}\\ \frac{\mathrm{\τ}}{f}\end{array}\right],$

$d^{\left(n\right)}=\left[\begin{array}{c}{d}^{\left(1\right)}\\ d^{\left(2\right)}\\ .\\ .\\ .\\ d^{\left(n\right)}\end{array}\right]\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\hat{D}}^{\left(1\right)}-D^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}-D^{\left(2\right)}\\ .\\ .\\ .\\ {\hat{D}}^{\left(1\right)}-D^{\left(n\right)}\end{array}\right]$

Can further obtain:

${\widehat{\mathrm{\Θ}}}^{\left(n\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(n\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(n\right)}\end{array}\right]={\left({\left[B^{\left(n\right)}\right]}^T{B}^{\left(n\right)}\right)}^{-1}{\left[B^{\left(n\right)}\right]}^T{A}^{\left(n\right)}$ (formula 8)

the n time estimated value that represents Θ, changes with the passing of n, and estimated accuracy successively improves, for the n time estimated value of CM to CH timing parameter.

Thus, CM obtains the n time estimated value to CH local clock: wherein, t _cMfor bunch member's local zone time.

The 3rd step, the clock essence based on HLCC is synchronous:

If certain the cluster internal memory at cognitive radio networks (is denoted as CM two bunches of members _aand CM _b), CM _aand CM _bclock synchronous initialization and the thick synchronizing process of clock to CH are all completed respectively.Without loss of generality, establish CM _aand CM _ball receive N CHB message.If need to set up HLCC between them to support follow-up communication task, they can use the algorithm (this type of algorithm can adopt effective scheme of the prior art, does not belong to the scope of discussing herein) that crosses of the control channel with time synchronized condition to set up for CM in current available frequency spectrum cavity-pocket _aand CM _bavailable HLCC.In the process of establishing of HLCC, CM _aand CM _bbetween can complete mutual clock essence synchronizing process, detailed process is:

CH continue by LLCC periodically to whole bunch of transmission with local transmitting time cHB message, now, n ∈ N+1, N+2 ..., N+m}, m is natural number.CM _areceive CHB message, read data, and record local time of reception cM _breceive broadcast, read transmitting time and record receives local zone time meanwhile, CM _band CM _abetween periodically attempt exchange control signal message (cycle is identical with CHB broadcast cycle).If CM _bto CM _asend one with local zone time with corresponding CHB message transmitting time send request (Request To Send, RTS) message.If CM _areceive this RTS message, the local zone time that recording messages arrives and read the time data in message with according to cM _afrom local data base, find the time of advent corresponding to this CHB message transmitting time cM _ato CM _bsend one with local zone time with and transmission license (Clear To Send, CTS) message.If CM _breceive CTS message, sign in and readout time data with

For some moment n ∈ N+1, N+2 ..., N+m}, CM _b, CM _aand the relation between CH three's local clock is as follows.

$\left\{\begin{array}{c}{t}_A=f_A\·t_{\mathrm{CH}}+{\mathrm{\τ}}_A\\ t_B=f_B\·t_{\mathrm{CH}}+{\mathrm{\τ}}_B\end{array}\right.$ (formula 9)

Wherein, f _arepresent cluster head CH and bunch member CM _aclock skewing, f _brepresent cluster head CH and bunch member CM _bclock skewing, t _arepresent bunch member CM _aclock, t _brepresent bunch member CM _bclock, τ _arepresent cluster head CH and bunch member CM _aclock skew, τ _brepresent cluster head CH and bunch member CM _bclock skew, t _cHrepresent cluster head clock;

Two formulas are merged into above:

T _a=t _bφ ₁+ φ ₂(formula 10)

Wherein, θ _a, θ _brepresent respectively bunch member CM _awith a bunch member CM _bcorresponding timing parameter; Make θ _a=1/f _a, θ _b=1/f _b; ${\mathrm{\φ}}_1\stackrel{\mathrm{\Δ}}{=}{f}_A/f_B={\mathrm{\θ}}_B/{\mathrm{\θ}}_A,{\mathrm{\φ}}_2\stackrel{\mathrm{\Δ}}{=}{\mathrm{\τ}}_A-{\mathrm{\τ}}_B{f}_A/f_B={\mathrm{\τ}}_A-{\mathrm{\τ}}_B{\mathrm{\φ}}_1;$ Therefore, φ ₁, φ ₂be called CM _awith CM _bbetween relative time clock parameter; Further, obtain the relation of corresponding time data as follows:

$(T_{2,A}^{\left(n\right)}-{\mathrm{\τ}}_A)/f_A=T_1^{\left(n\right)}+D_A^{\left(n\right)}$ (formula 11)

$(T_{2,B}^{\left(n\right)}-{\mathrm{\τ}}_B)/f_B=T_1^{\left(n\right)}+D_B^{\left(n\right)}$ (formula 12)

$(T_4^{\left(n\right)}-{\mathrm{\τ}}_A)/f_A-D_{\mathrm{BA}}^{\left(n\right)}=(T_3^{\left(n\right)}-{\mathrm{\τ}}_B)/f_B$ (formula 13)

$(T_5^{\left(n\right)}-{\mathrm{\τ}}_A)/f_A+D^{\mathrm{AB}}=(T_6^{\left(n\right)}-{\mathrm{\τ}}_B)/f_B$ (formula 14)

Wherein with represent respectively from CM _ato CM _bwith from CM _bto CM _apropagation delay.Can get (formula 13) and (formula 14) is added and obtained

$T_4^{\left(n\right)}+T_5^{\left(n\right)}=(T_3^{\left(n\right)}+T_6^{\left(n\right)}){\mathrm{\φ}}_1+2{\mathrm{\φ}}_2$ (formula 15)

(formula 11) and the difference of (formula 12) are added to (formula 15) obtains

$\begin{array}{c}{T}_4^{\left(n\right)}+T_5^{\left(n\right)}+T_{2,A}^{\left(n\right)}=\\ (T_3^{\left(n\right)}+T_6^{\left(n\right)}+T_{2,B}^{\left(n\right)}){\mathrm{\φ}}_1+3{\mathrm{\φ}}_2+(D_A^{\left(n\right)}-D_B^{\left(n\right)})f_A\end{array}$ (formula 16)

Notice (formula 11) and (formula 12) for all n ∈ 1,2 ..., the N} moment also sets up, and after therefore they being subtracted each other, obtains:

$T_{2,A}^{\left(n\right)}=T_{2,B}^{\left(n\right)}\·{\mathrm{\φ}}_1+{\mathrm{\φ}}_2+(D_A^{\left(n\right)}-D_B^{\left(n\right)})f_A,n\∈\{1,2,...,N+m\}$ (formula 17)

(formula 16) and (formula 17) write as to matrix form

P ^(m)=Q ^(m)Φ ^(m)+ ξ ^(N+m)(formula 18)

Wherein

$P^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_{2,A}^{\left(1\right)}\\ .\\ .\\ .\\ T_{2,A}^{\left(N\right)}\\ T_4^{(N+1)}+T_5^{(N+1)}+T_{2,A}^{(N+1)}\\ .\\ .\\ .\\ T_4^{(N+m)}+T_5^{(N+m)}+T_{2,A}^{(N+m)}\end{array}\right],Q^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{cc}{T}_{2,B}^{\left(1\right)}& 1\\ .& .\\ .& .\\ .& .\\ T_{2,B}^{\left(N\right)}& 1\\ T_3^{(N+1)}+T_6^{(N+1)}+T_{2,B}^{(N+1)}& 3\\ .& .\\ .& .\\ .& .\\ T_3^{(N+m)}+T_6^{(N+m)}+T_{2,B}^{(N+m)}& 3\end{array}\right]$

${\mathrm{\Φ}}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\mathrm{\φ}}_1^{\left(m\right)}\\ {\mathrm{\φ}}_2^{\left(m\right)}\end{array}\right],{\mathrm{\ξ}}^{(N+m)}=\left[\begin{array}{c}{\mathrm{\ξ}}^{\left(1\right)}\\ {\mathrm{\ξ}}^{\left(2\right)}\\ .\\ .\\ .\\ {\mathrm{\ξ}}^{(N+m)}\end{array}\right]\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}(D_A^{\left(1\right)}-D_B^{\left(1\right)})f_A\\ (D_A^{\left(2\right)}-D_B^{\left(2\right)})f_A\\ .\\ .\\ .\\ (D_A^{(N+m)}-D_B^{(N+m)})f_A\end{array}\right]$

Can obtain:

${\widehat{\mathrm{\Φ}}}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}\\ {\widehat{\mathrm{\φ}}}_2^{\left(m\right)}\end{array}\right]={\left({\left[Q^{\left(m\right)}\right]}^T{Q}^{\left(m\right)}\right)}^{-1}{\left[Q^{\left(m\right)}\right]}^T{P}^{\left(m\right)}$ (formula 19)

represent CM _awith CM _breceive after the N+m time cluster head broadcast CM _awith CM _bbetween the m time relative time clock estimates of parameters.

So far, CM _bcomplete CM _athe estimation of local relative time clock parameter.In like manner, CM _aalso can obtain CM _bthe estimation of local relative time clock parameter.

According to the m time Φ estimates of parameters, can obtain CM _bto CM _abe estimated as for the m time of local clock ${\hat{t}}_{A,B}^{\left(m\right)}=t_B{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}+{\widehat{\mathrm{\φ}}}_2^{\left(m\right)}.$

This is CM _awith CM _bbetween clock based on HLCC essence synchronizing process.

The beneficial effect that adopts the present invention to obtain:

The present invention sets up the control channel of cognitive radio networks with clock synchronous and organically combines.Owing to can continue to obtain the global synchronized timing system information that time synchronization process provides in the process of establishing of control channel, so can accelerate the process of establishing of control channel; Time synchronization process of the present invention is obtaining after the support of two-forty control channel, can exchange more efficiently local time information, thereby improves constantly the precision of time synchronized.The invention provides a kind of effectively cognitive radio networks method for synchronizing time, improved the availability of cognitive radio networks at network establishment stage, contribute to cognitive radio networks to move towards practical.

Brief description of the drawings

Fig. 1 is the cognitive radio networks clock synchronizing method flow chart based on double-deck control channel mechanism;

Fig. 2 is the cognitive radio networks clock synchronous first step based on double-deck control channel mechanism and the message schematic diagram of second step;

Fig. 3 is the message schematic diagram of cognitive radio networks clock synchronous the 3rd step based on double-deck control channel mechanism.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Fig. 1 is the cognitive radio networks clock synchronous flow chart based on double-deck control channel mechanism.Whole flow process is divided into three steps.

The first step, the level based on LLCC finds and the concrete step of clock initialization is (n=1).

(1) a certain cognitive user CU waits for the broadcast of cluster head CH at LLCC, if the broadcast of CH do not detected, this cognitive user sends CHB message (No. ID and local transmitting time comprising this CU by LLCC ), announce oneself to be cluster head CH.

(2) a certain CU receives the broadcast from CH, and the cognitive user that sends CHB message is made as CH by this CU, will oneself take a bunch of member CM of this CH as, and from CHB message, read CH local zone time data and the time of advent of recording CHB message return to a RTJ message to CH simultaneously, and by the ID of oneself and local zone time data write in this message.

(3) CH receives the RTJ message from certain CU by LLCC, recording messages time of advent and from this message, read ID number, this CU is made as to a member of this bunch.

(4) CH replys CTJ message by LLCC to CM, and by the local transmitting time of oneself with the RTJ message time of advent of record write in this message.

(5) this CM receives the CTJ from CH by LLCC, recording messages time of advent and read the time in message with thus, CM obtains the estimation initial value to CH local clock parameter and CHB message propagation time delay:

$X=\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}\end{array}\right]={\left({\left[B^{\left(1\right)}\right]}^T{B}^{\left(1\right)}\right)}^{-1}{\left[B^{\left(1\right)}\right]}^T{A}^{\left(1\right)}.$

(6) CM obtains the initial estimate to CH local clock:

${\hat{t}}_{\mathrm{CH}}^{\left(1\right)}=t_{\mathrm{CM}}\·{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}-{\widehat{\mathrm{\θ}}}_2^{\left(1\right)}.$

Second step, the thick synchronous concrete steps of clock based on LLCC be described below (n={2 ..., N}).

(1) CH utilizes LLCC periodically to send CHB message, wherein with local zone time data

(2) CM receives CHB message, and the note local reception time is and read the CH local zone time data in message

(3) CM estimates the timing parameter of CH, obtains with computing formula is shown in (formula 8).

(4) CM obtains the estimated value to CH local clock:

The 3rd step, the synchronous concrete steps of clock based on HLCC essence following (n={N+1 ..., N+m}).

(1) CH continues to send CHB message on LLCC, wherein with local zone time data

(2) CM _aand CM _bon LLCC, receive CHB message, read and record respectively time of reception and be with

(3) CM _bon HLCC to CM _asend with local zone time with the CH time rTS message.

(4) CM _aon HLCC, receive RTS message, sign in and read the time data in RTS message with according to cM _afrom local data base, find the corresponding CHB message time of advent

(5) CM _ato CM _bsend one with local zone time with and cTS message.

(6) CM _breceive CTS message, record reaches the time and read with

(7) CM _bobtain CM _athe estimated value of relative time clock parameter with computing formula is shown in (formula 19).

(8) calculate CM _bto CM _athe estimated value of local clock be

Fig. 2 is the cognitive radio networks clock synchronous first step based on double-deck control channel mechanism and the message schematic diagram of second step.As shown in the figure, the local clock of CH and CM is expressed as time shaft t _cHwith t _cM, both clock offset are τ, CM is f with respect to the clock skewing of CH.The first step, exchanges CHB, CMB and CHA message successively between CH and CM, corresponding message transmitting time is respectively with the message sink time is respectively with second step, CH periodically sends CHB message to CM, and transmitting time is n ∈ [2, N], time of reception is n ∈ [2, N].

Fig. 3 is the message schematic diagram of cognitive radio networks clock synchronous the 3rd step based on double-deck control channel mechanism.In figure, CH, CM _aand CM _blocal clock be expressed as time shaft t _cH, t _awith t _b.T _awith t _cHclock offset be τ _a, t _bwith t _cHclock offset be τ _b.CMA is f with respect to the clock skewing of CH _a, CM _bbe f with respect to the clock skewing of CH _b.CH periodically sends CHB message, and transmitting time is made as cM _aand CM _bthe local zone time that receives CHB message is made as respectively with cM _aand CM _bbetween exchange successively RTS and CTS signaling message.CM _bplace, the local zone time that sends RTS message is made as the local zone time that receives CTS message is made as cM _aplace, the local zone time that receives RTS message is made as the local zone time that sends CTS message is made as said n ∈ N+1, N+2 ..., N+m}, m is natural number.

Above embodiment is only unrestricted for technical scheme of the present invention is described, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and do not depart from aim and the scope of technical solution of the present invention, all should be encompassed in the middle of claim scope of the present invention.

Claims (6)

1. the cognitive radio networks clock synchronizing method based on double-deck control channel mechanism, is characterized in that comprising the steps:

If represent the cluster head local zone time of the n time cluster head broadcast, n is natural number; If in given user bunch, comprise at least one cognitive user in cognitive radio networks;

The first step, the neighbours/level based on low layer control channel is found and clock synchronous initialization;

(S11) step, establishes some cognitive user and waits for cluster head broadcast at low layer control channel, if cluster head broadcast do not detected, determines that this cognitive user is cluster head;

(S12) step, cluster head sends cluster head broadcast by low layer control channel, comprises No. ID and local transmitting time of this cognitive user in cluster head broadcast

(S13) step, the cognitive user except cluster head reads the time from cluster head broadcast and the time of advent of recording cluster head broadcast simultaneously return to the message or exit request message of joining request to cluster head, described in join request message or exit No. ID and the local transmitting time that request message comprises cognitive user

(S14) step, cluster head is received the message or exit request message of joining request from certain cognitive user by low layer control channel, and records this message time of advent now, cognitive user is denoted as a bunch member; Then, reply one to a bunch member who sends this message and comprise local transmitting time allow add message or allow exit message;

(S15) step, bunch member receives that allowing that cluster head in (S14) step replys adds message or allow after exit message, record local time of advent and read the time with by calculating the estimation initial value to cluster head timing parameter and bunch broadcast propagation delay

(S16) step, bunch member, by calculating the estimated value to cluster head clock, completes the clock synchronous initialization between bunch member and cluster head;

Second step, the clock based on low layer control channel is slightly synchronous;

(S21) step, cluster head periodically continues to send N-1 cluster head broadcast by low layer control channel, and comprises local transmitting time data in transmission message wherein, n={2 ..., N}, N is more than or equal to 2 natural number;

(S22) step, a bunch member receives cluster head broadcast, records local time of reception to be and read the time

(S23) step, the estimation initial value in conjunction with bunch member who obtains in the first step to cluster head local clock parameter Estimation initial value and bunch broadcast propagation delay, upgrades the timing parameter estimated value of bunch member to cluster head;

(S24) step, upgrades the estimated value of bunch member to cluster head local clock;

The 3rd step, the clock essence based on high-rise control channel is synchronous;

Be located in certain cluster of cognitive radio networks and have two bunches of members, be denoted as respectively CM _aand CM _b, and they have completed respectively the clock synchronous initialization of the described first step with cluster head and the clock of second step is slightly synchronizeed;

(S31) step, cluster head continues to send cluster head broadcast on low layer control channel, and in message with local zone time wherein, n ∈ N+1 ..., and N+m}, m is natural number;

(S32) step, CM _aand CM _bon low layer control channel, receive cluster head broadcast, read and record respectively time of reception and be with

(S33) step, CM _bon high-rise control channel to CM _asend with local zone time with the cluster head time send a request message;

(S34) step, CM _aon high-rise control channel, receive CM _bsend a request message, sign in and read the time data in sending a request message with according to cM _afrom local data base, find the corresponding cluster head broadcast time of advent

(S35) step, CM _ato CM _bsend one with with local transmitting time transmission grant message;

(S36) step, CM _breceive transmission grant message, record the local time of advent and read with

(S37) step, calculates CM _bwith CM _abetween the estimated value of relative time clock parameter;

(S38) step, calculates CM _bto CM _athe estimated value of local clock, completes CM _awith CM _bbetween clock based on high-rise control channel essence synchronizing process.

2. a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism as claimed in claim 1, is characterized in that (S15) step in the first step, and compute cluster member is to cluster head local clock parameter Estimation initial value estimation initial value with bunch broadcast propagation delay be specially:

$\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(1\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(1\right)}\\ {\hat{D}}^{\left(1\right)}\end{array}\right]={\left({\left[B^{\left(1\right)}\right]}^T{B}^{\left(1\right)}\right)}^{-1}{\left[B^{\left(1\right)}\right]}^T{A}^{\left(1\right)},$

Wherein, $A^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_1^{\left(1\right)}\\ T_4^{\left(1\right)}\\ T_5^{\left(1\right)}\end{array}\right],B^{\left(1\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{ccc}{T}_2^{\left(1\right)}& -1& -1\\ T_3^{\left(1\right)}& -1& +1\\ T_6^{\left(1\right)}& -1& -1\end{array}\right].$

3. a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism as claimed in claim 1, is characterized in that the concrete computational process of (S23) step in second step is:

${\widehat{\mathrm{\Θ}}}^{\left(n\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\θ}}}_1^{\left(n\right)}\\ {\widehat{\mathrm{\θ}}}_2^{\left(n\right)}\end{array}\right]={\left({\left[B^{\left(n\right)}\right]}^T{B}^{\left(n\right)}\right)}^{-1}{\left[B^{\left(n\right)}\right]}^T{A}^{\left(n\right)},$

Wherein, $A^{\left(n\right)}=\left[\begin{array}{c}{T}_1^{\left(1\right)}+{\hat{D}}^{\left(1\right)}\\ T_1^{\left(2\right)}+{\hat{D}}^{\left(1\right)}\\ .\\ .\\ .\\ T_1^{\left(n\right)}+{\hat{D}}^{\left(1\right)}\end{array}\right],B^{\left(n\right)}=\left[\begin{array}{cc}{T}_2^{\left(1\right)},& -1\\ T_2^{\left(2\right)},& -1\\ .& .\\ .& .\\ .& .\\ T_2^{\left(n\right)},& -1\end{array}\right],$

represent the n time estimated value of Θ, n={1 ..., N}, for timing parameter estimated value.

4. a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism as claimed in claim 1, is characterized in that the concrete computational process of (S24) step in second step is: wherein, represent the n time estimated value of the local clock of bunch member to cluster head, t _cMfor bunch member's clock value, for timing parameter estimated value.

5. a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism as claimed in claim 1, is characterized in that (S37) step computing formula in the 3rd step is:

${\widehat{\mathrm{\Φ}}}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}\\ {\widehat{\mathrm{\φ}}}_2^{\left(m\right)}\end{array}\right]={\left({\left[Q^{\left(m\right)}\right]}^T{Q}^{\left(m\right)}\right)}^{-1}{\left[Q^{\left(m\right)}\right]}^T{P}^{\left(m\right)},$

Wherein,

$P^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{c}{T}_{2,A}^{\left(1\right)}\\ .\\ .\\ .\\ T_{2,A}^{\left(N\right)}\\ T_4^{(N+1)}+T_5^{(N+1)}+T_{2,A}^{(N+1)}\\ .\\ .\\ .\\ T_4^{(N+m)}+T_5^{(N+m)}+T_{2,A}^{(N+m)}\end{array}\right],Q^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}\left[\begin{array}{cc}{T}_{2,B}^{\left(1\right)}& 1\\ .& .\\ .& .\\ .& .\\ T_{2,B}^{\left(N\right)}& 1\\ T_3^{(N+1)}+T_6^{(N+1)}+T_{2,B}^{(N+1)}& 3\\ .& .\\ .& .\\ .& .\\ T_3^{(N+m)}+T_6^{(N+m)}+T_{2,B}^{(N+m)}& 3\end{array}\right],$

represent CM _awith CM _breceive after the N+m time cluster head broadcast CM _awith CM _bbetween the m time relative time clock estimates of parameters.

6. a kind of cognitive radio networks clock synchronizing method based on double-deck control channel mechanism as claimed in claim 1, is characterized in that (S38) step computing formula in the 3rd step is: CM _bestimate CM _alocal clock ${\hat{t}}_{A,B}^{\left(m\right)}\stackrel{\mathrm{\Δ}}{=}{t}_B{\widehat{\mathrm{\φ}}}_1^{\left(m\right)}+{\widehat{\mathrm{\φ}}}_2^{\left(m\right)},$ Wherein, for CM _awith CM _bbetween the m time relative time clock estimates of parameters.